Re: GRDGRADIENT
"J. Luis" <[email protected]>
| Newsgroups | gmane.comp.gis.gmt.user |
|---|---|
| Message-ID | <[email protected]> |
Except that your grid has the Z positive down so it's actually dipping SW > > Hi, > I used grdgradient to determine the strike of downdip direction as per > the last suggestion from GMT-HELP: > > *grdgradient slabsurf2.grd=nf/-1 -D -Gslabslope.grd -M* > > I got the following results: > > -70.5395348837 -16.5490196078 224.041519165 > -70.4651162791 -16.5490196078 224.033538818 > -70.3906976744 -16.5490196078 223.925460815 > -70.3162790698 -16.5490196078 223.353469849 > -70.2418604651 -16.5490196078 222.613449097 > -70.1674418605 -16.5490196078 220.593399048 > -70.0930232558 -16.5490196078 218.752716064 > -70.0186046512 -16.5490196078 213.890182495 > > Since the slab is subducting towards east at normal dip (30 degree) > and according to my slab image, the downdip direction in this > latitude/longitude range should be in the range of 20-80 degree but I > am getting more than 200 degree. I have also attached the my slab map > for the reference. I would grateful for any suggestion. > > Thanks > Abhash kumar > University of North Carolina at Chapel Hill > ------------------------------------------------------------------------ > *From:* J. Luis <[email protected]> > *Sent:* Thursday, February 20, 2014 6:35 PM > *To:* World-Wide GMT Usage and Help Mailing List > *Cc:* Mr Abhash Kumar > *Subject:* Re: [GMT-HELP] GRDGRADIENT > > OK, I downloaded the SA slab from http://earthquake.usgs.gov/data/slab/ > > cut a sub region, tested with GMT and Mirone, and had to dig in my > code to find out why grdgradient in Mirone is giving the right result > but not on command line. It turns out that (and I don't remember why) > one has to multiply z by -1 before computing the "aspect" (that is > what you are looking for). > Note that you don't want the slope, so don't use -S . The following > gives the correct result > > grdgradient sam_slab.grd=nf/-1 -D -Gaspect.grd -M > > Joaquim > > > > >> Hi, >> >> I used grdgradient to calculate the strike of downdip direction at >> every grid point of the subducting slab: >> >> >> *grdgradient slabsurf2.grd -Dn -Sslabgradient.grd -M -V* >> >> >> I am getting the following results: >> >> >> -69.9441860465 -17.0522875817 35.6361160278 >> -69.8697674419 -17.0522875817 36.5936279297 >> -69.7953488372 -17.0522875817 37.6132316589 >> -69.7209302326 -17.0522875817 38.6617622375 >> -69.6465116279 -17.0522875817 34.4591636658 >> -69.5720930233 -17.0522875817 31.943397522 >> -69.4976744186 -17.0522875817 31.6246490479 >> -69.423255814 -17.0522875817 30.8437995911 >> >> >> I roughly know that the strike of downdip direction should vary in >> the range of 30degree-120 degree in this region. Do I need to use >> some more functions to calculate the reasonable strike direction. I >> urgently need to calculate this and would be extremely grateful for >> any suggestions. >> >> >> Thanks >> >> Abhash kumar >> >> University of North Carolina at Chapel Hill >> >> To unsubscribe, send the message "signoff gmt-help" to >> [email protected] > To unsubscribe, send the message "signoff gmt-help" to [email protected]